During illness weight loss occur but 500gram weight loss in 5.5kg baby is too much...
You should give calories dense food, add ghee or butter and guve more carbohydrates food...also give fruit juice....these all should be start after 6completed months..
Continue BF....
Weight should be compared with birth weight...so at 5months weight should be double of birth weight...
Next Steps
consult online if requires...
Health Tips
dont worry...give proper diet so baby will regain the weight..